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Ancient wonder It may be great for curing a splitting headache, but scientists have now discovered that aspirin also activates an enzyme that burns fat, a finding that could unlock its cancer fighting properties, according to a new study.

Previous research has shown that once ingested, aspirin breaks down into salicylate, a compound derived from plants such as willow bark, and used as a drug for thousands of years. Ancient Egyptians recorded the medicinal use of willow bark in their manuscripts.

In the 1890s, pharmaceutics developed a modified form of salicylate to make it less irritating to the stomach - creating the drug aspirin.

More recently, research has known that salicylate triggers a molecular pathway that leads to pain relief.

Now a team led by Professor Grahame Hardie, a cell biologist at the University of Dundee in Scotland, has discovered how salicylate affects metabolism. They report their findings today in the journal Science.

Hardie and his team suspected that salicylate affected an enzyme known as AMPK, which is a key regulator of cell metabolism.

To test this, researchers compared a control group of mice, with another group that lacked a sub-unit of the AMPK enzyme. They injected both groups of mice with salicylate and measured the rate at which they utilised fat.

They found that the mice with AMPK were able to burn fat at a faster rate. This indicated that salicylate switches on AMPK, increasing the breakdown of fat.

"It's exciting that we've discovered salicylates are working in a new and different way to what we originally thought," says Hardie.

Implications for cancer

Hardie says recent studies have shown that people who take aspirin over long time periods appear to have a lower incidence of cancer. But doctors warn against prolonged aspirin use, which can cause stomach bleeding.

"I'm particularly interested in these protective effects against cancer," says Hardie. "Further research may help us discover another way of taking salicylate, other than aspirin, which has fewer side-effects."

He explains that anti-cancer effects may be due to the activity of AMPK, as diabetic drugs that target AMPK in cells are also associated with a reduced incidence of cancer.

Dr Briony Forbes, a biochemist at the University of Adelaide, says findings in this study are likely to explain recently identified protective effects against cancer by aspirin.

"The surprising finding that salicylate promotes AMPK activity also opens up exciting avenues for diabetes prevention and treatment."